1. Field of the invention
The present invention relates to wireless communication, and more particularly, to a method for controlling channel access of a station (STA) by an access point (AP) in a wireless local area network system and an apparatus for supporting the same.
2. Related Art
Recently, various wireless communication technologies have been developed with the development of information communication technology. Among them, a wireless local area network (WLAN) is a technique allowing mobile terminals such as personal digital assistants (PDAs), lap top computers, portable multimedia players (PMPs), and the like, to wirelessly access the Internet at homes, in offices, or in a particular service providing area, based on a radio frequency technology.
A technology related to a WLAN system has been spotlighted as a wireless communication technology providing a high speed data service in an unauthorized band. Particularly, unlike an existing cellular communication system, when an access point (AP) serving as a base station is connected only to a wired network including a distribution system and a power supply, the access point may be easily installed by anyone, has a cheap cost, and may perform data communication. Therefore, the access point has been generalized.
After the institute of electrical and electronics engineers (IEEE) 802 which is a standardization organization of a WLAN technology was established on February, 1980, a number of standardization operations have been conducted. An initial WLAN technology has supported a speed of 1 to 2 Mbps in frequency hopping, spread spectrum, infrared communication, or the like, using a frequency of 2.4 GHz through the IEEE 802.11. Recently, a speed up to 54 Mpbs may be supported by applying orthogonal frequency division multiplex (OFDM). In addition, in the IEEE 802.11, various technology standards such as improvement of quality of service (QoS), access point protocol compatibility, security enhancement, radio resource measurement, wireless access for a vehicular environment, fast roaming, a mesh network, interworking with an external network, wireless network management, and the like, have been put to practical use or have been developed.
In addition, as a technology specification relatively recently established in order to overcome a limitation for a communication speed that has been pointed out as a disadvantage in the WLAN, there is an IEEE 802.11n. An object of the IEEE 802.11n is to increase a speed and reliability of a wireless network and extend an operating distance of the wireless network. More specifically, the IEEE 802.11n is based on multiple inputs and multiple outputs (MIMO) technology in which multiple antennas are used at both of a transmitting end and a receiving end in order to support a high throughput (HT) having a maximum data processing speed of 540 Mbps or more, minimize a transmission error, and optimize a data speed. Further, in this specification, a coding scheme of transmitting several overlapped duplicates may be used in order to increase data reliability, and an orthogonal frequency division multiplexing (OFDM) scheme may also be used in order to increase a speed.
The characteristics of the WLAN system differentiated from other wireless communication systems perform communication using a shared wireless medium to support a channel access method based on a contention based medium access. That is, wireless apparatuses supporting the WLAN are not controlled by a channel access order and/or ranking that is a wireless medium but access a medium by contention therebetween.
Meanwhile, there may be a wireless apparatus that is set to implement the channel access unlike the general wireless apparatus for supporting the WLAN. When the above-mentioned abnormal wireless apparatuses and the general normal wireless apparatuses contend each other for accessing the channel, collision occurs therebetween, such that the normal channel access cannot be performed. Therefore, a need exists for a method and an apparatus for supporting normal channel access of the wireless apparatuses in the WLAN system in which the abnormal wireless apparatuses and the normal wireless apparatuses set for accessing the channel differently from the general channel access rules coexist.